Liquification of gas



Sept. 18, 1962 w. R. cRooKs ErAL 3,054,259

LIQUIFICATION OF GAS Original Filed June 29, 1956 2 Sheets-Sheet 2 TURB BOOSTER INVENTORS MR. C ecoles BY J' F01. EM/wu yawn/ 3,054,269 LIQUIFICATION F GAS William R. Crooks and John Fullemann, Mount Vernon, Ohio, assignors to The Cooper-Bessemer Corporation, Mount Vernon, Ohio, a corporation of Ohio Original application June 29, 1956, Ser. No. 594,808, now Patent No. 2,929,548, dated Mar. 22, 1960. Divided and this application Feb. 17, 1960, Ser. No. 9,239 3 Claims. (Cl. 62-9) This invention relates to a method of liquifying a gas with the aid of a high speed turbocompressor.

It has heretofore been considered impractical to build centrifugal compressors in a size range to handle gas flows much below 800 c.f.rn. because of excessive gas friction in the narrow impeller passages that are required in so small a unit, and also because the speed of rotation is so high that the lubrication of bearings, gears and couplings becomes a major concern. Further, a centrifugal compressor operating at speeds higher than 20,000 rpm'. to 30,000 r.p.m. presents a problem in connecting it to a power source, such as an electric motor or an internal combustion engine because it cannot be directly driven, but must be coupled to the power source by gearing or the like which will impart the necessary high rotative speed to the compressor from the low rspeed prime mover.

Where small flows of air or gas in the order of 15 c.f.m. to 200 c.f.rn. are desired at pressure ratios of more than 1.5 to 1, compression has always been accomplished by reciprocating machine. The present invention makes it possible to utilize a rotating machine even for these small tlows. The present invention is shown and described herein in an embodiment in which small flows at high pressures are produced.

The primary object of the present invention is to provide an improved method of liquifying gases by the use of a small, high speed turbocompressor.

Other objects and advantages of the invention will become apparent from the following specification, reference being had to the accompanying drawings, in which:

FIG. 1 is a central vertical `sectional View of a modified turbocompressor suitable for use in the machine shown in FIG. 2; and

FIG. 2 is a circuit diagram of a process for the manufacture of liquid oxygen in which turbocompressors constructed in accordance with the present invention are used.

A simple form of tur-bocompressor suitable for a method according to the invention is Ishown in FIG. .1. As there shown, a center stator element 211 is provided which is counterbored at its center to receive a balance collar 212 in the form of a thick walled tube of carbon or other low friction material. The outer surface of the tube is stepped as at 213 to seat in the stator at a definite axial location. At one end of the bore of the tube, a series of axial grooves 214 provide communication with a pressure chamber 215 which is formed in the bore `by relieving a portion of the rotor shaft as hereinafter described. The grooves 214 are, in effect, continuations of radial grooves 216 formed in an end face of the bushing or collar 212, which grooves communicate with a source of gas under a pressure higher than any pressure existing at the opposite end of the rotor -so that the tlow of gas is always in the same direction from end to end of the bore of the collar or bushing.

The rotor, in the form shown, comprises a compressor wheel 2117 and a turbine wheel 218 connected by a shaft 219. The rotor shaft fits the diameter of the collar or bushing very closely except for a relieved portion 220 which, with the adjacent stationary surface, forms the pressure chamber 215.

The rotor spins on an air bearing and centers itself in the bore of the bushing or collar 212, seeking its own States Patent ice" axis of balance. Axially, the rotor is held in position by the flow of air from one end to the other and if the rotor tends -to move to close off the space between the back of the turbine wheel 218 and the adjacent surface of the collar 212, the restriction to fiow of air out of chamber 2115 will cause the pressure to increase and cause the rotor to move outwardly to reestablish the proper flow space. The pressure drop across the end of the collar 212 in this instance is the difference between the compressor discharge pressure ("110 p.s.i.g.) and the turbine inlet pressure which is about 42 p.s.i.g'. In this for-rn also, the effective areas of the inner and outer faces of the two wheels and the pressures existing thereon are equated at the respective ends of the rotor.

FIG. 2 shows schematically a system for the liquification of oxygen in which turbocompressors according to the present invention are advantageously employed. As there shown, gas is taken into a iirst stage reciprocating compressor 300 and compressed, passing then to a rst centrifugal booster 302 driven by a turbine 303. The booster 302 and turbine 303 form a turbocompressor constructed in accordance with the present invention and may be made specifically as shown in FIG. 1, since the energy extracting portion, or turbine, may be single stage. From the booster 302 the gas passes through a heat exchanger 304 to a -second reciprocating compressor stage 305. Repeated stages of compression in reciprocating units, coupled with boosting in centrifugal units, followed by cooling in heat exchangers brings the gas at relatively high pressure and medium temperature to a final point where a portion of the gas is split off to expand successively in the turbines of the turbocompressor units while the remainder passes through an expansion valve 310 to a collection tower 31151 in which the oxygen is collected at low temperature and low pressure, the temperature being so low that the oxygen exists as a liquid. The temperatures, pressures and iiow volumes at the several points in the cycle or states are as shown in the following table. On the drawing the states are designated by encircled letters, the lead lines running to the pipes or conduits in which the gas in the designated state exists. It will be noted that the iiow of gas in cubic feet per minute is very small in certain of the stages; far below that which can be successfully passed through known rotary machines. It will also be noted that the energy extracted from the gas for operation of the turbines not only lowers the temperature of the `gas but is returned to the system in the form of energy of compression in the booster units.

Table I Flow Pressure Temp. Temp. Flow 0.1m. at

State (p.s.l.a.) R.) F.) (lbs.) actual conditions I. 863 852 392 530 262 J- 858 570 110 530 192. 5 K 3, 025 815 355 530 58. 2 L 3,010 570 110 530 38. 8 M 2, 975 500 40 530 32. 9 N 2, 970 500 40 265 16. 5

This is a division of United States application Serial No. 594,808, Iune 29, 1956, now Patent No. 2,929,548

for Turbocompressor.

Various modifications of the above described embodi U ment of the invention and, 4in particular, of the turbocompressor can be made without departing from the scope of the invention, if such modifications are within the spirit and tenor of the appended claims.

We claim:

1. A method of liquifying gas which comprises compressing a supply of gas, in a first stage of a main compressor, feeding the gas to a compressor portion of a first turbocompressor to compress the gas further, cooling the gas to a temperature approximating that of the gas before compression, further compressing the gas in a sequential stage of the main compressor, feeding the gas to a compressor portion of another turbocompressor to compress the gas still further, again cooling the gas, repeating the last three steps until the gas is compressed to a predetermined pressure with the temperature thereof approximating that of the gas before compression, dividing the gas into two portions, expanding a rst portion of the gas to lower the temperature and the pressure thereof, directing a second portion of the compressed gas sequentially through tur-bine portions of said turbocompressors in the reverse order in which the gas was fed to them during compression to drive said turbocompressors and to eX- pand the second portion to lower the temperature and the pressure thereof, and recombining the first and the second portions of the gas.

2. Apparatus for liquifying a gas comprising a multistage reciprocating compressor, means for feeding gas to be liquied to a iirst stage of said reciprocating compressor, a rst turbocompressor having a turbine portion and a compressor portion, means for lfeeding the gas from the rst stage of said reciprocating compressor to said compressor portion, means for cooling the compressed gas, means for feeding the compressed gas to a sequential stage of said reciprocating compressor, an additional turbocompressor having a turbine portion and a compressor portion, means for feeding gas from said sequential stage of said reciprocating compressor to the compressor portion of said additional turbocompressor, means for dividing the gas into two portions after being compressed by said reciprocating compressor and said turbocompressors, an expansion valve, means for feeding one portion of the gas through said expansion valve to lower thc ternperature and the pressure thereof, and means for feeding the other portion of the gas sequentially through said turbine portions of said turbocompressors to drive said cornpressor portions and to lower the temperature and the pressure of said other portion of the gas to approximately the reduced pressure of the gas emerging from said expansion valve.

3. Apparatus according to claim 2 wherein said turbocompressors have connecting shafts between the turbine portions and the compressor portions and means for effecting a flow of gas around said connecting shafts from said compressor portions toward said turbine portions for rotatably supporting said shafts.

References Cited in the le of this patent UNITED STATES PATENTS 2,509,034 Clator et al May 23, 1950 2,529,880 McClure Nov. 14, 1950 2,705,406 Morrison Apr. 5, 1955 2,713,781 Williams July 26, 1955 2,799,997 Morrison July 23, 1957 2,922,285 Rae Jan. 26, 1960 2,941,374 Morrison June 21, 1960 FOREIGN PATENTS 735,906 Germany lune 1, 1943 

